An electronic expansion valve is an important component forming a refrigeration system, and is a fundamental component in the refrigeration system, besides an evaporator, a compressor and a condenser. Operating process of the electronic expansion valve is generally as follows: with energizing and de-energizing of a coil device, open degree of a valve opening is adjusted by a valve needle, so as to adjust the flow of refrigerant.
In the prior art, an electronic expansion valve is disclosed in the Chinese Patent No. 200580023202.7. Referring to FIG. 1, it is a structural schematic view of an electronic expansion valve in the prior art.
As shown in FIG. 1, the electronic expansion valve in the prior art includes a valve seat 1′. A sleeve part 2′ is provided inside the valve seat 1′ and includes a guiding part 2′1 and a head 2′2. A gear seat 3′ is hermetically supported by the head 2′2. A gear system 8′ is provided in the gear seat 3′. The gear system 8′ is transmissively connected to a rod screw 4′. As shown in FIG. 1, an upper end of the gear seat 3′ is further hermetically connected to a motor shell 5′1, inside of which a motor 5′ is provided. The motor 5′ is transmissively connected to the gear system 8′ via an output shaft. A slidable valve rod 6′ is provided inside the guiding part 2′1. A nut 7′ extends from an upper end of the valve rod 6′ and is further provided in a limit part 3′1 in a lower cavity of the gear seat 3′. Due to the limit action of the limit part 3′1, the nut 7′ can axially slide in the limit part 3′1, and cannot circumferentially rotate.
In operation, the motor 5′ is started, and its output shaft is rotated. The rotation motion is thus transmitted to the screw rod 4′ via the gear system 8′. Since the screw rod 4′ extends into the nut 7′ via thread engagement, and the nut 7′ only can axially slide in the limit part 3′1 and cannot rotate circumferentially, the nut 7′ can slide axially as the screw rod 4′ rotates, and then the nut 7′drives the valve rod 6′ to axially slide in the guiding part 2′1, so as to adjust the open degree of the valve opening.
However, the above electronic expansion valve in the prior art has disadvantages as follows.
Firstly, the upper end of the gear seat 3′ is hermetically connected to the motor shell 5′1 via thread engagement, and the lower end of the gear seat 3′ is hermetically connected to the head 2′2 of the sleeve part 2′ via thread engagement. Therefore, there are two sealed parts. The more the number of the sealed parts is, the higher the leakage probability is. Besides, the assembly structure is complicated.
Secondly, the nut 7′ extends from the upper end of the valve rod 6′, and is engaged with the limit part 3′1 such as to limit the circumferential rotation of the valve rod 6′. However, since the nut 7′ has to extend from the upper end of the valve rod 6′, the overall valve core component has a larger axial dimension, which causes a larger axial dimension of the valve body. Furthermore, since the outer diameter of the nut 7′ is significantly less than that of the valve rod 6′, the overall valve core component has a large lower portion and a small upper portion. Therefore, in manufacturing process of components, the inner diameter of the head 2′2 of the sleeve part 2′ is less than that of the guiding part 2′1, and the outer diameter of the lower end of the gear seat 3′ has to be reduced, so that the limit part 3′1 with a smaller inner diameter can be mounted in an inner cavity of the gear seat 3′. It can thus be known that the sleeve part 2′ and the gear seat 3′ each have a complicated structure, which causes difficult processing and high manufacturing cost. Also, since the valve core component formed of the nut 7′ and the valve rod 6′ has a large lower portion and a small upper portion, the assembling process of the nut 7′, the valve rod 6′, the gear seat 3′, the sleeve part 2′ and the valve seat 1′ is complicated and difficult.
Therefore, it becomes an urgent problem to be addressed by the person skilled in the art to improve the electronic expansion valve in the prior art, so as to reduce leakage probability thereof and simplify assembly structure thereof.